Headlight.



W. CHURCHILL.

HEADLIGHT.

APPLICATION FILED NOV. 25, 1910.

Patented Aug. 6, 1912.

oooooof v UNITED STATES PATENT OFFICE.

, mm CHURCHILL, F (WRITING,- NEW-YOK!- nnanmon'r.

To all wlwm it may concern:

Be it known that I, WILLiAM'CnURcnmL, a citizen of the -Uni ted States,resid n at Corning, in the county of Steuben and tate of New York, haveinvented certain new and useful Improvements in- Headlights, of whichthe following is a pecification.

This invention relates to improvements in headlights for locomotives,trolley cars, automobiles, and the like; and my object is to provide aheadlight, particularly when of high candle power,.in which those lightwaves, which now render these headlights objectionable, will be cut outfrom the beam of light projected from the headlight.

It is well known that relatively long light waves, e. 9., red andyellow, are transmitted through semi-opaque media more readily thanrelatively short light waves, 0. 9., green, blue, and violet. The bestknown illustration of this fact is the color of the sun or moon whenrising or setting, as seen through tog, dust laden atmosphere and smoke.In operating a vehicle of any description provided with a headlight,such as a locomotive, trolley car, automobile, or a motor boat, throughfog and smoke, a beam of high candle power is of little or noassistance, for the reason that the glare of light reflected back fromthe fine particles of fog or smoke into the eyes of the operator rendersit impossible to see objects in his path at any distance. I havediscovered by experiment that most of the light producing this glareconsists of the light waves having the shorter wave lengths. To increasethe penetration of headlights in fog and smoke, I propose to use ascreen of yellow translucent material, such as yellow tinted glass,which will cut oil the shorter wave lengths by absorption, and allow thelonger wave lengths to pass through unimpeded. This will reduce therange somewhat under clear weather conditions, but with a headlight ofhigh candle power there is usually more light than is required at suchtimes, while in fog and smoke the light is of little or no value. Inusing this yellow screen the penetration in fog and smoke can beincreased very perceptibly. Furthermore, a yellow light is less glaringby far to the eye than a blue or bluish light, since the iris of the eyecontracts and thereby protects the retina when looking at a yellowlight, while it contracts very little, if at all, for blue or bluishlight. This is a well known physioapumimm of team mum. aj mdam mamummas, mm. Serial no. men.

Patented Aug. 6, 1912.

logical principle. A' yellow headlight is far less glaring, e. 9 lessdazzling to an observer looking at or approachi the same than is thecase with a white or b uish white light. To oneapproa'ching a vehiclecarry ing a headlight of this character it is absolutely impossible tosee beyond or back of the approaching light; whereas, with a yellowscreen interposed, the range of vision will pass on beyond the light sothat objects back of the approaching vehicle. will be discernible.

In carryin out in invention I propose either to ma e the ront glass orthe lens of the headlight of the yellow glass, or to interpose eitherbehind or in front of the said glass or lens a separate screen of theyellow glass, which may be made removable, so that the screen may beused or not, as may be desired.

By way of' illustrating the application of my invent-ion I have shown inthe accompanying drawings sectional views of two types of headlights, inwhich Fi ure 1 presents a headlight having a paraholic reflector and asimple glass front; and Fig. 2, a headlight havin a reflector of glassor metal, and a lens in ront.

In Fig. l the source of illumination is shown as an acetylene flameissuing from the burner l, the light rays from which are projectedforward from the parabolic reflector 2, the beam of light passingthrough the simple glass front 3. In carrying out my invention thisglass front instead of being made of clear glass, will be made of ayellow glass of a suitable shade to absorb green, blue. and violet lightwaves with the least possible effect upon the red and yellow. The yellowglass used by me is transparent and shows transmission of both red andyellow light practically equal to that obtained with an ordinary whiteglass, and at the same time absorbs all of the blue and violet waves andall of the green of relatively shorter wave length, It is impossible tocut ofl all of the green, but the more detrimental portion is entirelyabsorbed. Instead, however. of making this yellow screen perma nent inthe lamp, I may so construct the lamp that a screen of the yellow glass,as shown at 4, may be removably placed therein, the lamp being soarranged that the screen may be fastened in front of the glass 3, orbehind it. As shown in Fig. 1 the screen is positioned behind the frontglass,

' closing of the front door.

and is adapted to be held in position by the InrFig. 2 the burner 1 isproperly positioned between a reflector 5 and a lens 6 which, in theillustration is shown to be of .to one side,,asb mounting it upon an arm8 pivotally 'at-tac ed to a projection 10, at-

tached toth'e burner tube, the thumb screw 9 being provided to holdthearm in the desired position upon said projection.

For locomotlves in particular, where acetylene or high candle powerelectric light is tohe used in the headlights, it will be preferable tomake the front glass or lens of the yellow glass, as there is no reasonfor providing a removable screen, and the interposition of a second(glass medium through which the light must pass has the disadvantage ofcutting down the ower of the light, and I believe that it W11 be foundpreferable in nearly, if not all, cases to use the one medium instead oftwo. J

The advantages of the yellow glass are particularly marked with an arelight or acetylene flame, owing to the large proport' of blue rayspresent; but it may also be e ployed to advantage where the blue raysfrom the. source of light are at a minimum, as in a kerosene or otheroil flam What I claim, therefore, as my invention and desire to secureby Letters Patent is 1. A headlight provided. with a yellow glass screenin the path of the rays of light adapted to transmit practically'undimin ished' the total amount of red and yellow light "waves producedbythe source of illumination and at the same time to absorb all of theblue and violet waves and all of the green of relatively shorter wavelength.

2. A headli ht provided with a yellow glass screen a apted to be placedin or out of the path of the rays of light and to transmit practicallyundiminished the total amount of red and yellow light waves roduced bythe source of illumination an at the same time to absorb all of the blueand Jiolet waves and all of the green of relatively shorter wave length.

In testimony whereof I have afiixed my signature, in presence of twowitnesses.

WILLIAM CHURCHILL. Witnesses M. E. VERBECK, EUGENE

